A search operation is under way or a border guard official missing after a patrol boat sank off Ukraine's port city of Mariupol following an explosion, the border guard said.
One crew member died and five others were being treated for injuries in the incident., police were quoted as saying by Interfax news agency.
The cause of Sunday's explosion was not immediately clear, authorities said.
Mariupol is on the edge of the conflict between government forces and Russian-backed separatists and has been under threat from rebel attacks for months.
"At 14.20 hours (local time) a patrol boat exploded as it came out of its mooring station in Mariupol," a state border guard statement said.
"There were seven service staff on board. The search is continuing for one service staff member."
